Hydrosilylation reaction curable silicone compositions form cured products having excellent properties such as weathering resistance and heat resistance, and are therefore used in a variety of applications. However, such compositions exhibit poor adhesive properties. As a result, curable silicone compositions containing adhesion-imparting agents have been proposed. For example, Japanese Unexamined Patent Application Publication No. 2008-528788 proposes a curable silicone composition that contains an acryloxy functional alkoxysilane or a methacryloxy functional alkoxysilane, an alkenyl functional silanol terminated organopolysiloxane and an epoxy functional alkoxysilane; and Japanese Unexamined Patent Application Publication No. 2010-248384 proposes a curable silicone composition that contains a silane coupling agent having two alkoxy groups directly bonded to a silicon atom in a molecule and at least one type of coupling agent selected from among a boron coupling agent, a titanium coupling agent, an aluminum coupling agent and a zirconium coupling agent.
The curable silicone composition proposed in Japanese Unexamined Patent Application Publication No. 2008-528788 relates to a coating composition for a synthetic fiber material, and does not indicate or suggest that it is possible to solve the problem of a cured product obtained from the composition exhibiting reduced adhesive properties and transparency over time under conditions of high temperature and high humidity by combining the specified alkoxysilane and alkenyl functional silanol terminated organopolysiloxane.
In addition, the curable silicone composition proposed in Japanese Unexamined Patent Application Publication No. 2010-248384 has the problem of a cured product obtained from the composition exhibiting reduced adhesive properties and transparency over time under conditions of high temperature and high humidity. As a result, using the present composition as a sealing agent or adhesive for an optical semiconductor element leads to the problem of significantly reduced optical semiconductor device reliability under conditions of high temperature and high humidity.
An object of the present invention is to provide a curable silicone composition that forms a cured product which exhibits excellent initial adhesive properties and transparency and exhibits excellent adhesive durability and retention of transparency under conditions of high temperature and high humidity. A further object of the present invention is to provide this type of cured product. A further object of the present invention is to provide an optical semiconductor device having excellent reliability that uses this type of cured product.